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Validation of Diagnostic Methods for European Foulbrood on Commercial Honey Bee Colonies in the United States
Meghan O'Grady Milbrath1, Peter Daniel Fowler2, Samuel K Abban3
1Department of Entomology, Michigan State University, 4090 N. College Road, Pollinator Performance Center, RM 100, Lansing, MI 48910, USA.
Abstract:
One of the most serious bacterial pathogens of Western honey bees (Apis mellifera Linnaeus [Hymenoptera: Apidae]) is Melissococcus plutonius, the cause of the disease European foulbrood. Because European foulbrood is highly variable, with diverse outcomes at both the individual and colony levels, it is difficult to diagnose through visual inspection alone. Common lab diagnostic techniques include microscopic examination and molecular detection through PCR. In 2009, a lateral flow device was developed and validated for field diagnosis of European foulbrood. At the time, M. plutonius was thought to be genetically homogenous, but we have subsequently learned that this bacterium exists as multiple strains, including some strains that are classified as 'atypical' for which the lateral flow device is potentially less effective. These devices are increasingly used in the United States, though they have never been validated using strains from North America. It is essential to validate this device in multiple locations as different strains of M. plutonius circulate in different geographical regions. In this study, we validate the field use of the lateral flow device compared to microscopic examination and qPCR on larval samples from 78 commercial honey bee colonies in the United States with visual signs of infection. In this study, microscopic diagnosis was more sensitive than the lateral flow device (sensitivity = 97.40% and 89.47%, respectively), and we found no false positive results with the lateral flow device. We find high concurrence between the three diagnostic techniques, and all three methods are highly sensitive for diagnosing European foulbrood.
Insights
This study validated a field diagnostic test for European foulbrood in honey bees. Microscopic examination proved more sensitive than the lateral flow device, though both methods showed high accuracy in detecting Melissococcus plutonius.
Area of Science:
- Apiculture
- Bacteriology
- Veterinary Entomology
Background:
- European foulbrood, caused by Melissococcus plutonius, is a significant honey bee disease.
- Diagnosis is challenging due to disease variability and the existence of atypical bacterial strains.
- A lateral flow device (LFD) for field diagnosis exists but requires validation with diverse M. plutonius strains.
Purpose of the Study:
- To validate the field efficacy of a lateral flow device for diagnosing European foulbrood.
- To compare the LFD's performance against microscopic examination and qPCR.
- To assess diagnostic accuracy using North American M. plutonius strains.
Main Methods:
- Larval samples from 78 US commercial honey bee colonies with visual signs of infection were tested.
- Diagnostic methods included microscopic examination, qPCR, and the lateral flow device.
- Results were compared to determine sensitivity and concurrence between techniques.
Main Results:
- Microscopic diagnosis demonstrated higher sensitivity (97.40%) than the lateral flow device (89.47%).
- No false positive results were observed with the lateral flow device.
- High concurrence was found between all three diagnostic methods, indicating overall high sensitivity.
Conclusions:
- The lateral flow device is a useful tool for diagnosing European foulbrood, but microscopic examination offers superior sensitivity.
- Validation with diverse M. plutonius strains is crucial for accurate field diagnostics.
- Combined diagnostic approaches ensure reliable detection of Melissococcus plutonius infections.
